DESCRIPTION: (Applicant's Abstract) The proposed investigation seeks to examine the use of "club" drugs among gay /bisexual men in New York City (NYC) and build upon the previous work of the investigators. We will undertake a longitudinal investigation guided by the following three aims: (1) to determine the individual differences and changes in club drug use among gay/bisexual men in NYC over the course of one year; (2) to determine the extent to which antecedent person factors, contextual factors, and coping factors explain differences in year-long club drug use trajectories of gay/bisexual men in NYC; and (3) to determine how individual changes in club drug use over the course of a year, in combination with antecedent person factors, contextual factors, coping factors, explain differences in sexual risk-taking patterns in the course of one year among gay/bisexual men in NYC. Our work will be guided by cognitive escape theory as we seek to determine how antecedents of club drug use influence the use of these substances, and how the interaction of these antecedents with actual use of club drugs leads to cognitive disengagement and sexual risk taking in terms of HIV infection and potentially reinfection. Our work will focus on five club drugs used primarily by gay/bisexual men in NYC: cocaine, GFIB, ketamine, MDMA, and methamphetamine. We will recruit 450 men into our investigation and undertake assessments of the antecedents, club drugs use, and sexual risk-taking behaviors 4 times over the course of one year, and utilize univariate and multivariate growth curve modeling to determine the relationships between these factors as a mean of undertaking theory testing; this will be complemented by our use of qualitative techniques, using the Critical Incident Measure, to provide us with episode-specific data to help realize the relationships that we are assessing as well as further develop the theory of cognitive escape. Our work will be conducted entirely with a community-based sample of seropositive, seronegative, and serostatus unknown gay/bisexual men and through our affiliations with the numerous mainstream gay venues, public sex environments, and community based organization that serve gay/bisexual men in NYC.